This invention relates to an apparatus for longitudinally slitting a continuous web, and more particularly to such an apparatus in which a lower, circular cutter or cutters mounted on a shaft journaled on a machine frame for rotation are capable of being axially shifted to accommodate various web widths to be slit.
Apparatus for longitudinally slitting a traveling web of paper, foil, cloth, plastic, metal or like material, may employ the known straight cut or looped cut approach. In the looped cut technique, the web to be slit into individual strips travels tangentially between at least one top and at least one bottom circular blade so that at least two strips may be slit from a single web. Usually, several upper and lower balde pairs are employed for slitting a relatively wide web into a plurality of relatively narrow strips.
Webs of various widths are often desired by the end processor of the web to be slit. Thus, a relatively wide web must be slit during one production process, for example into relatively wide webs, and during another production process into relatively narrow webs. These slitted webs are usually rewound into rolls for easy handling and processing by the end processor.
Since the needs of the end processor may change, a relatively wide web may need to be subdivided into more narrow webs thereby requiring the slitting apparatus to be reset. This process is usually referred to as "positioning."
During the straight cut approach it is relatively simple to position the bottom and top cutting blades, since the web does not bear against one of the blade pairs so as to impede positioning. However, during the looped cut approach, it is more difficult to shift the lower blade or blades embraced by the web which presses against the lower blade or blades due to web tension which normally predominates in the web for processing purposes. The movability of the lower blade or blades along the support shaft is therefore limited, such that special provisions must be made to facilitate easier axial adjustment of the lower blade or blades.
U.S. Pat. No. 3,583,270 discloses a slitter apparatus for traveling webs in which the lower cutters are driven by their own motors and are capable of being shifted over the width of the web to be cut to the desired position by means of an air cushion introduced to provide air bearings between the motor platform and transversely extending rails.
In published PCT application WO 83/02083 a cutting device is disclosed in which the support hub of the cutting blade is enlarged by means of pressurized hydraulic fluid, annular chambers or grooves at the inner circumferential surface of the hub being provided for this purpose.
French Pat. No. 2,340,170 discloses a similar cutting device in which the support hub of a circular cutter is enlarged as pressurized hydraulic fluid is directed into an open groove at the inner circumferential surface of the hub.